This invention relates generally to transmission lines, and more particularly, to microstrip and stripline transmission lines for electronic devices. The transmission lines may be used as part of wireless communications circuitry in handheld electronic devices, as an example.
Handheld electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type.
Due in part to their mobile nature, handheld electronic devices are often provided with wireless communications capabilities. Handheld electronic devices may use wireless communications to communicate with wireless base stations. For example, cellular telephones may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz (e.g., the main Global System for Mobile Communications or GSM cellular telephone bands). Handheld electronic devices may also use other types of communications links. For example, handheld electronic devices may communicate using wireless networking technology bands such as the 2.4 GHz and 5 GHz band used in the WIFI® (IEEE 802.11) wireless networking technology and the 2.4 GHz band used in the BLUETOOTH® wireless networking technology. Communications are also possible in data service bands such as the 3G data communications band at 2170 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System).
To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices. At the same time, manufacturers are continually striving to maximize the performance of wireless communications circuitry and antennas. As one example, manufacturers have made attempts to route transmission lines such as microstrip and stripline transmission lines through the potentially complex geometry of small form factor products while maximizing the efficiency of the transmission lines.
When transmission lines are routed through complex geometry of small form factor products, manufacturers may desire to bend the transmission lines at sharp angles (e.g., a small bend radius may help minimize wastes space inside a small form factor housing). Because a typical transmission line includes relatively stiff ground planes formed from solid copper, it can be difficult or impossible to bend the rigid transmission line at all desired angles. Manufacturers have attempted to alleviate some of the problems of these rigid transmission lines by forming flexible transmission lines that have ground planes formed from cross-hatched lines of copper. The cross-hatched lines of copper, however, include gaps in the ground plane that lead to less effective grounding and a less efficient transmission line.
It would therefore be desirable to be able to provide improved transmission lines such as microstrip and stripline transmission lines for electronic devices.